Preparation And Properties Of Nanoporous Lithium Ion Battery Anode Materials

This dissertation was mainly devoted to the synthesis of porous lithium ion battery anode materials. The content can be divided into two parts. The first part was using metal organic framework (MOF) as precursors to synthesize metal oxide with nano and porous structure:First, different particle sizes of dodecahedron precursors were synthesized by controlling the polarity of the solution. Through the results of scanning electron microscope (SEM) images, it can be found that different particle sizes of precursors present obvious edge angles and their morphology can be well retained after annealing. X-ray diffraction (XRD) measurements suggested that the annealed polyhedral products were pure single-phase NiCo2O4. When tested as lithium-ion battery anode,0.5 ?m NiCo2O4 polyhedra exhibited a specific capacity of 1050 mAh g-1 at 0.1 A g-1 after 60 cycles.Second, Ni-Fe bimetallic oxide nanotubes with a hollow and porous structure were synthesized by using metal-organic framework (MOF) annealing process. The Ni/Fe molar ratios in the binary metal oxide were rationally designed. Typically, Nio.62Fe2.3gO4 (called NFO-0.25) nanotubes with a tube shell of around 10 nm possess a specific surface area of 134.3 m2 g-1 and were composed of nanosized primary particles. The lithium ion battery performance of the nanotube anode was evaluated by galvanostatic and rate cycling. In the half-cell, a high capacity of 1184 mAh g-1 for the NFO-0.25 anode was maintained at a current density of 0.25 A g-1 after 200 cycles.Third, we reported a simple route to synthesis nitrogen-doped mesoporous interlinked carbon/NiO nanosheet that consist of carbon nanosheets and monodisperse NiO nanoparticles embedded in them homogeneously. During the heat treatment, a large number of mesoporous were formed in the product with the evaporation (or thermal decomposition) of the organic ligand. When tested as an anode for lithium ion batteries, the unique structure of the mesoporous carbon/NiO showed a reversible capacity of 627 mAh g-1 at 0.5 A g-1 after 300 cycles. Moreover, the as-assembled carbon/NiO nanosheet supercapacitor could also exhibit an excellent cycling performance by combined the pseudocapacitive behavior of the NiO nanoparticles with the electric doublelayer capacitors (EDLCs) of the nitrogen-doped mesoporous carbon.The second part of the dissertation was based on the research our group. The polystyrene microspheres was using as a sacrifice and hard template to synthesize hollow carbon and hollow silica secondary template. And then with the help of those two kinds of secondary template, a series of core-shell materials were synthesized:At first, a core-shell composite composed of MoS2 nanosheets grown on hollow carbon microspheres was synthesized by a hydrothermal and a subsequent annealing route. The result shown that well-graphitized hollow-carbon@highly crystalline MoS2 (HC@MoS2) was obtained after the four-step reaction. And it was found that the synthesized MoS2 was consisted of 2H and 1T phases. The lithium storage property of the composite was investigated as an anode material for lithium-ion batteries. Benefited from the special morphology and structure, a stable capacity of 970 mAh g-1 for over 100 cycles at a current density of 0.25 A g-1 was realized on the material. Even at a high current density of 4 A g-1, a reversible capacity as high as 560 mAh g-1 was delivered. Moreover, the reasons for the excellent electrochemical performance of the material were explored and discussed in detail.And second, a series of double layer nanopheres (DLNs), such as Mn2O3, Co3O4, NiO, NiCo2O4, and MnCo2O4 have been successfully synthesized through a general template method. The layers of DLNs were assembled by different nanostructure units and the removing of the SiO2 template formed a void of several ten nanometers between the double layers, resulting large specific surface areas for them. The energy storage performances of the as-prepared DLNs were further investigated in lithium ion batteries and supercapacitors. Based on their unique nanostructures, the DLNs exhibited excellent electrochemical performance with long cycle stability and high specific capacities or capacitances. The best performance, DLNs-NiCo2O4 delivered a reversible capacity of 1107 mAh g-1 at 0.25 C after 200 cycles in lithium ion battery system, and showed a capacitance of 1088 F g-1 with capacitance loss of less than 3% at 5 A g-1 after 5000 cycles in supercapacitors.